Founding Member

I need an electrical guru here.
I am totally lost, and while I have a understanding of the electrical system, it is NOT my best area of knowledge once you get into a serious gremlin. I am handy with a test light, but that's about it.

I have gone through all the basics, like replace this, test that, and check wire connections. I have also tried 4 CCRMs total in the last 24 hours.... The stock one, a used crusty stock one from the u-pull, a used (but new looking) Ford parts counter replacement CCRM from the u-pull, and a brand new CCRM last night when we got desperate. They all acted totally the same. They ran every function that they were supposed to run, except the fan, on either speed, for any reason.

So, right now this is where we stand:
*1994 GT
*The circuits involved all remain stock.
*Wires visible all appear undamaged, connections tight.
*New CCRM is currently installed. We still have the original and the Ford brand replacement as well. The crusty 94 OEM box was used for the core charge and is no longer in our hands.
*The fan works fine when jumped straight to a 12v power source, ruling out failure of the fan unit itself.
*New ECT installed. Still have the old one, kept it just incase.

Some testing and observations:
Fan works with direct 12v applied.
60a Fan maxi-fuse has power on both sides.
Used a test light on the fan when it was supposed to be running, in order to rule out bad connection at plug, and no power to the plug.
CCRM replaced as noted.
Turning on the a/c will NOT run the fan.
Chip is tuned to turn the fan on at 180*, but we ran it with and without the tuning just to make sure it wasn't a chip problem.

There is a 10a regular fuse in the power distribution box under the hood that it's name sounds like it might be connected to the fan operation. It does not have power to either side of the fuse, or either connection when the fuse is removed from the block. I am not sure that it even should, or ever has had power to it. (Key on, key off, or running, it's the same result.) Fuse is good. Just for giggles, since that 10a fuse had no power to it, I put 12v to the feed side of the fuse... Nothing happened except my son said the CEL flashed when I applied the juice. I know this was not a sound test procedure, but I figured if it's a fuse in the power distribution box, it can handle 12v and it's not like it's one of the circuits with 5v going to the PCM or any sort of 'fragile' circuit. Doesn't matter nothing happened, no sparks, and checking the circuit for a short with a test light came up negative. The CEL may have been coincidental.

I have access to a code reader, but not until later this morning.
If that shows anything, I'll post it. The last time I used my son's code reader on the 94, it tested the fan by running it, and it checked out, but that was a month or two ago, before the fan symptoms came about.

Now that you are thoroughly confused like me, I'll throw in one other strange observation:
The fan began running in low speed all the time, like the relay was stuck in the on position about 2 weeks ago. It ran all the time like this for a week, and now it hasn't run at all in about it week.

I just assumed this assured it was the CCRM... I figured the relay was stuck on, and then when it finally shut off, it has been stuck off. Problem solved, replace CCRM. Didn't work.

Any help that doesn't involve looking at schematics? I looked at those for the fan/CCRM, and got completely befuddled, just like any time I try to understand a wiring diagram.

Based on what I've seen in another post that I found and after looking at a diagram, the EDF and HEDF relays receive power and ground from the PCM.

On the fan/60A side, since the fan runs when voltage is applied, you can assume that the ground for the fan itself is good. Your problem on the fan side could be an open wire from the 60A fuse in the box to the CCRM or an open wire from the CCRM to the fan itself. You can shoot wires from the fuse box to pins 3 and 4 on the CCRM. You can also shoot from pins 1 and 2 (low speed) and pins 6 and 7 (high speed) from the CCRM to the fan motor.

It looks like the HEDF relay receives ground from the PCM. You can check the ground wire by shooting from pin 32 at the PCM to pin 17 in the CCRM.

Most of my wiring experience comes from working on aircraft. The ones I'm used to honestly aren't usually as detailed. I hope some of this helps a little bit.

SN Certified Technician

I have the feeling that your EDF driver(s) simply went sour. If you want (and haven't yet), confirm the fan is not being commanded on (12V at pin 14 above ~208*F; continuity to ground at Pin 17 above 226* or with AC on. You've tested that AC part already). This test is useful because it rules out the CCRM since those commands are ahead of the CCRM.

BTW, what you saw with the EDF-fuse characteristics in the underhood fusebox is normal.

You might end up doing away with the stock control and either use your own stand-alone controller or integrate another thermo-switching mechanism to the stock relays.

Founding Member

I have the feeling that your EDF driver(s) simply went sour. If you want (and haven't yet), confirm the fan is not being commanded on (12V at pin 14 above ~208*F; continuity to ground at Pin 17 above 226* or with AC on. You've tested that AC part already). This test is useful because it rules out the CCRM since those commands are ahead of the CCRM.

BTW, what you saw with the EDF-fuse characteristics in the underhood fusebox is normal.

You might end up doing away with the stock control and either use your own stand-alone controller or integrate another thermo-switching mechanism to the stock relays.

Click to expand...

New question:Is it possible for just one or two functions to crap out on the ECM? Making it a "bad" unit, but only for some functions?

I spent hours today going from the ECM to the CCRM, to the fan, and through every single connector, making sure all the connections were clean, tight, and wires from point a to point b undamaged in any way. Everything works, everything is hooked, nothing is dirty, corroded, or burnt. I even reseated and tightened grounds. I'd have cleaned them, but none were dirty... none were even loose, but I loosened, reseated, and tightened them anyway.

I added a chassis ground of my own to the ECM case, just to be sure it wasn't having trouble grounding through the stock sliver of metal in the plastic sleeve.

The codes were "failed fan" and "failed secondary fuel pump" (Whatever that is???) Both codes were re-occurring too. I'd erase them, and they'd come back right away.

Fact is that the fan works, everything checks out on the CCRM, it's just that the ECM doesn't seem to be able to tell the fan to come on. It either thinks it is telling it, or it lacks the ability to tell it. So I can only assume, with all lines of communication open, that the ECM just isn't using them for whatever reason... Failure inside the ECM?

Founding Member

I have the feeling that your EDF driver(s) simply went sour. If you want (and haven't yet), confirm the fan is not being commanded on (12V at pin 14 above ~208*F; continuity to ground at Pin 17 above 226* or with AC on. You've tested that AC part already). This test is useful because it rules out the CCRM since those commands are ahead of the CCRM.

BTW, what you saw with the EDF-fuse characteristics in the underhood fusebox is normal.

You might end up doing away with the stock control and either use your own stand-alone controller or integrate another thermo-switching mechanism to the stock relays.

Click to expand...

One other question...
The car has a chip.
It's an SCT 4 bank.
Is it possible to reinstall the "drivers" into the ECM with the chip?
I get the same failure with the chip turned on or off.
The only thing I didn't try was total removal of the chip.
Bama says it was tuned for 180 fan turn on.
Does that mean that the chip is driving the fan?
Or does the chip just modify the temperature signal to the ECM, making the ECM want to turn the fan on using the ECM's drivers?
Therefore if the drivers are bad, then the chip can tell it to do things all it wants, but the ECM can't. ???
Is that kinda where we are, assuming the ECM is the problem?

I have an aftermarket thermostatic switch on the shelf. I bought it for another project but never used it. I don't have an issue with the mechanics of how to install it, but I do have this stubborn mental roadblock to doing so because dammit, the car is supposed to being doing that, and I don't want to duplicate something the car is supposed to be doing for itself... It's the principle of the thing!

(BTW, Thank you on the idea to check the signal BEFORE the CCRM, I haven't done that, and will tomorrow, and that will confirm my theory for sure.)

SN Certified Technician

Yep, situations similar to yours are not uncommon. They can even pass the self-test (and function properly during said test) even though they don't perform properly in an operating dynamic.

Had you disconnected the ECT before generating the fan code (disconnecting the ECT can cause the fan code)? On the flip-side, disconnecting the ECT should command the low-speed fan to engage constantly.

I like fixing stuff for the challenge, and that said, most of the time it's not worth trying to pursue - there are better control methods available anyways.

At a minimum, I would add switches so you can manually activate the low and/or high speed fan.

SN Certified Technician

Re post 6 (you posted while I postulated), the chip should just modify the OEM settings and the ECM is driving the cart (drivers).

The chip adds a wildcard because you don't know what was programmed exactly (unless you have a bin file from the tuner). A hypothetical: If high speed was set to come on at 180, low might have been turned off altogether. Sometimes the failures involve only low-speed engaging with the AC, so if low is disabled, there could be no fan with the AC on (in that particular failure scenario).

Doing the pin 12 and pin 17 test (note your temp thresholds will be different/lower because of the chip) will be interesting and provide more direction (or confirm the direction we've been going).

Founding Member

Based on what I've seen in another post that I found and after looking at a diagram, the EDF and HEDF relays receive power and ground from the PCM.

It looks like the HEDF relay receives ground from the PCM. You can check the ground wire by shooting from pin 32 at the PCM to pin 17 in the CCRM.

Click to expand...

If I decide to use external triggers as inputs to the CCRM, it sounds like you are saying I need to trigger the EDF relay with 12v positive, and the HEDF relay with 12v ground?

I just need to find one wire going IN to the CCRM from the ECM for each relay (total 2), and splice the new and improved signal into each of those wires, abandoning the ECM side of those 2 wires?

My thought is to install a thermo switch to send 12v positive to the wire going from the ECM to the CCRM EDF input (cutting the ECM side loose of course, so it doesn't get the 12v positive and be potentially harmed, of course.)

Then to operate the HEDF, I would trigger a relay with 12v positive from the A/C system, and have switched portion of the relay grounded, so when activated, it grounded the wire formerly coming in from the ECM to the CCRM HEDF relay input.

Do I have a pretty good grasp of it?
I figure that this is the simplest way of going about it and taking advantage of all the wiring already there, instead of duplicating everything with external relays and wires. Basically use my own trigger signals to mimic the signals that should have come from the ECM.

Founding Member

Yep, situations similar to yours are not uncommon. They can even pass the self-test (and function properly during said test) even though they don't perform properly in an operating dynamic.

Had you disconnected the ECT before generating the fan code (disconnecting the ECT can cause the fan code)? On the flip-side, disconnecting the ECT should command the low-speed fan to engage constantly.

I like fixing stuff for the challenge, and that said, most of the time it's not worth trying to pursue - there are better control methods available anyways.

At a minimum, I would add switches so you can manually activate the low and/or high speed fan.

Click to expand...

You are sharp...
Yep. I disconnected the ECT yesterday in my diagnostic attempts, and it did store a code.
Something to the effect of "ECT value unexpected" (or similar).
When I unplugged it, the idle speed jumped up very high, which I didn't see coming.
It went from 800 to 2000 rpm (+/-)... and stayed there until I reinstalled the plug to the ECT.
The fan did not come on then either. The code reader explanation of this code was "Temperture in excess of 254* encountered".

The fan code has been constant. I can start all over, erase codes, whatever, and they (the secondary fuel pump circuit code too) come right back. I guess it is doing a "self check" when you power up the code reader and it starts cycling (clicking) all the relays and such? I know in the past, when the code reader powered up, and all the relays cycled, the fan came on for a moment, and it no longer does that. I no longer hear a relay cycle for that either, now that I think about it. I only hear 2 clicks anymore, it used to be at least 4.

Founding Member

Re post 6 (you posted while I postulated), the chip should just modify the OEM settings and the ECM is driving the cart (drivers).

The chip adds a wildcard because you don't know what was programmed exactly (unless you have a bin file from the tuner). A hypothetical: If high speed was set to come on at 180, low might have been turned off altogether. Sometimes the failures involve only low-speed engaging with the AC, so if low is disabled, there could be no fan with the AC on (in that particular failure scenario).

Doing the pin 12 and pin 17 test (note your temp thresholds will be different/lower because of the chip) will be interesting and provide more direction (or confirm the direction we've been going).

Click to expand...

Everytime I suspect the chip as causing a problem, I quickly dismiss it because of a few factors:

Trouble with the fan function, no matter if the tune is on, or bypassed with the switch.
Trouble with the fan function when the chip was out of the vehicle recently being retuned by BAMA.
Trouble with the fan function when the chip was in the car before the retune, which now it is like a whole different chip after the retune, and it has not changed anything.

The biggest thing that has changed since the beginning of the fan malfunction is that it began with the fan running when it wasn't supposed to, and then became a fan not running when it was supposed to. Both a clear malfunction, and the transition from the one malfunction state to the other malfunction state was seamless... It never went back to running correctly between states. It is not intermittent, and the biggest problem with it's current state, it cannot be driven this way. When the fan ran all the time, it could be driven...

Founding Member

Something just hit me after I wrote that last post...
If something 'stuck' inside the ECM that caused the fan to run constantly, could that cause an overload on the circuit-board or inside the ECM that finally caused a complete failure of the circuit? That makes it sound like a 'hardware' issue, instead of software, like drivers. The fan is not supposed to run constantly, and maybe the constant load caused a breakdown? Just a thought, I really don't have a clue if this is even possible, and one would think that there would be a fuse involved. ???

If I decide to use external triggers as inputs to the CCRM, it sounds like you are saying I need to trigger the EDF relay with 12v positive, and the HEDF relay with 12v ground?

I just need to find one wire going IN to the CCRM from the ECM for each relay (total 2), and splice the new and improved signal into each of those wires, abandoning the ECM side of those 2 wires?

My thought is to install a thermo switch to send 12v positive to the wire going from the ECM to the CCRM EDF input (cutting the ECM side loose of course, so it doesn't get the 12v positive and be potentially harmed, of course.)

Then to operate the HEDF, I would trigger a relay with 12v positive from the A/C system, and have switched portion of the relay grounded, so when activated, it grounded the wire formerly coming in from the ECM to the CCRM HEDF relay input.

Do I have a pretty good grasp of it?
I figure that this is the simplest way of going about it and taking advantage of all the wiring already there, instead of duplicating everything with external relays and wires. Basically use my own trigger signals to mimic the signals that should have come from the ECM.

Am I on the right track?

Click to expand...

That sounds about right to me. I'm not sure of the voltages sent to the EDF and HEDF by the PCM because I've only seen the diagram (haven't personally shot wires). What you're talking about here would just be a custom system that would do what the computer does and take it out of the equation.

It's making a little more sense to me, but I think HISSIN50 has a better grasp on this than I do. Nothing beats practical experience.

Founding Member

That sounds about right to me. I'm not sure of the voltages sent to the EDF and HEDF by the PCM because I've only seen the diagram (haven't personally shot wires). What you're talking about here would just be a custom system that would do what the computer does and take it out of the equation.

It's making a little more sense to me, but I think HISSIN50 has a better grasp on this than I do. Nothing beats practical experience.

Click to expand...

I guess I am essentially doing the software's job with hardware. Different method same result.
So now, instead of tuning the fan settings with the chip, I'll have to tune them via the thermostatic switch...
Back to the principle thing.... makes me mad I have to do what the car is supposed to do for itself, and what I am paying BAMA to do.
Oh well.... I am not going to outright buy a new ECM. I'll just wait for one to crop up, which will happen sooner or later. Someone that wants something I have, or owes me a favor, will have one eventually.

SN Certified Technician

If I decide to use external triggers as inputs to the CCRM, it sounds like you are saying I need to trigger the EDF relay with 12v positive, and the HEDF relay with 12v ground?

Click to expand...

Yeah, it's kind of a pain. You also end up using a third relay as a control (so low and high are not on at the same time - that's bad for the fan motor). I would not bother with all of that - I'd just run one Bosch/Tyco style 75 amp relay triggering high speed.

I just need to find one wire going IN to the CCRM from the ECM for each relay (total 2), and splice the new and improved signal into each of those wires, abandoning the ECM side of those 2 wires?

Click to expand...

Pin 14 receives 12V when low is commanded, and Pin 17 receives ground when high is commanded. If these wires are doing what they should (you'll test that tomorrow), you can do this. I have the feeling that one or both are not going to function properly however.

My thought is to install a thermo switch to send 12v positive to the wire going from the ECM to the CCRM EDF input (cutting the ECM side loose of course, so it doesn't get the 12v positive and be potentially harmed, of course.)

Then to operate the HEDF, I would trigger a relay with 12v positive from the A/C system, and have switched portion of the relay grounded, so when activated, it grounded the wire formerly coming in from the ECM to the CCRM HEDF relay input.

Click to expand...

This gets messy because you need a way to energize high if the temp continues to creep up (if low is insufficient and your AC is off), also while disengaging low speed. Back to needing 3 relays. You could try to reuse some of the OEM stuff, but personally, I would actually want my own circuits. The CCRM has a solid-state EDF control that we cannot do anything about. I like to have total control over circuits.

An alternative (though I know it's not the route you want to go. It's just an alternative) - The easiest way and requiring only one relay:

Grab your own relay. I would recommend a 75 amp unit, but a 30 amp SPST will work (keep a spare in your glovebox).

86: CCRM Pin 14 (supplying 12V when the EDF would come on).
To this lead (for the AC input), also splice in a wire going to the purple wire going into the LPCS (passenger firewall).
By utilizing this wire-source location, you get the *constant* signal to the relay. If you tap the circuit after the LPCS, the fan will cycle with the LPCS/AC clutch. OEMs have built-in hysteresis in these circuits, but you can't replicate that in a simple circuit like this.
In each of these leads (going to CCRM Pin 14 and to the AC/HVAC feed), place a diode to prevent backfeed.

85: to ground.
30: fused battery power.
87: to the high speed fan terminal.
As you can see, with a little rewiring, you could use either the EDF or HEDF relay for this circuit if you wanted.

SN Certified Technician

You are sharp...
Yep. I disconnected the ECT yesterday in my diagnostic attempts, and it did store a code.
Something to the effect of "ECT value unexpected" (or similar).
When I unplugged it, the idle speed jumped up very high, which I didn't see coming.
It went from 800 to 2000 rpm (+/-)... and stayed there until I reinstalled the plug to the ECT.
The fan did not come on then either. The code reader explanation of this code was "Temperture in excess of 254* encountered".

Click to expand...

Yeah, the ECT is a thermistor, so when reading almost no voltage (i.e. disconnected), that would correlate to a really high temperature. The ECU doesn't know what's up and goes into a sort of safe mode. Your idle goes high, the mixture goes rich, the EDF comes on, etc. The fan should have come on, unless something is preventing it.........

The fan code has been constant. I can start all over, erase codes, whatever, and they (the secondary fuel pump circuit code too) come right back. I guess it is doing a "self check" when you power up the code reader and it starts cycling (clicking) all the relays and such? I know in the past, when the code reader powered up, and all the relays cycled, the fan came on for a moment, and it no longer does that. I no longer hear a relay cycle for that either, now that I think about it. I only hear 2 clicks anymore, it used to be at least 4.

Click to expand...

Are you clearing codes from the KAM after a given code is set? If not, the codes you're seeing might be artifacts.

SN Certified Technician

Something just hit me after I wrote that last post...
If something 'stuck' inside the ECM that caused the fan to run constantly, could that cause an overload on the circuit-board or inside the ECM that finally caused a complete failure of the circuit? That makes it sound like a 'hardware' issue, instead of software, like drivers. The fan is not supposed to run constantly, and maybe the constant load caused a breakdown? Just a thought, I really don't have a clue if this is even possible, and one would think that there would be a fuse involved. ???

Click to expand...

Yeah, that's on me. I consider it a driver issue but it well could be hardware related. Very valid point and correction.

The circuits are not supplying hardly any current and the relays obviously do the heavy lifting. That said, something goes awry with a lot of the EDF/HEDF circuits, so maybe something does fry. I've not delved into an EEC to figure it out because I was not happy with the OEM fan control as it was.

The tests on CCRM pins 14 and 17 would show if a circuit was 'latched'. They seem to just go dead.

SN Certified Technician

That sounds about right to me. I'm not sure of the voltages sent to the EDF and HEDF by the PCM because I've only seen the diagram (haven't personally shot wires). What you're talking about here would just be a custom system that would do what the computer does and take it out of the equation.

It's making a little more sense to me, but I think HISSIN50 has a better grasp on this than I do. Nothing beats practical experience.

Click to expand...

It's nice having another set of eyes watching this in case I make an error. I haven't been on here in awhile and my old memory is foggy.

It's too bad that the OEM circuits use reverse polarity triggers because it makes creating an all-encompassing parallel fan circuit with one relay difficult.

SN Certified Technician

Final thoughts because we have a lot of loose ends (there are 10 ways to skin this cat). If you can supply 12V to CCRM PIn 14 OR ground to Pin 17 and the EDF or HEDF (respectively) engage, we can tailor a custom circuit around what, if any, circuits are functional. If one or both of those work, you can also rig up switches till a permanent solution is discovered.

Worst case, use your favorite fan control method and we can tailor a circuit around that. Most use a negative trigger, so we'd convert the AC input to a neg trigger and have all the switching be on the negative side.

Founding Member

Are you clearing codes from the KAM after a given code is set? If not, the codes you're seeing might be artifacts.

Click to expand...

Yes.
At first I wasn't, and it was throwing me off. I had old unerased codes that were rectified appearing to be current problems.
This only happened once. I caught on pretty quickly and erased them.

This gets messy because you need a way to energize high if the temp continues to creep up (if low is insufficient and your AC is off), also while disengaging low speed. Back to needing 3 relays.

Click to expand...

Good info.
This is why I need help with my electronics.
I know just enough about electrical to get into trouble!
I should realize that anytime something electrical seems so simple to fix, it usually isn't.

Founding Member

Hmmm...
Now that I think about it, I have some sort of triple relay on the shelf that came off a Volvo from the Ford years.
I grabbed it because I read somewhere they are great circuits for dual speed fans.
I bet this is the 3 relay circuit you are talking about.